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1. Field of the Invention
The present invention relates to hand tools, and more particularly, to an accessory for supporting and thereby enhancing the use and performance of hand tools during material processing of a substrate.
2. Description of the Related Art
Hand tools, especially power-assisted hand tools are well known and widely used in the construction, retrofitting or repair of solid surfaces and articles, such as by the selective removal of material in order to produce a desired contour, relief, conformation or shape as by grinding or sanding. For example, a builder may selectively grind a groove into a concrete surface to form a thermal relief, or sand some wood from a beam in order to produce a neat fit, or grind or sand away a contour to smooth or reconfigure a surface or edge. The procedure of such selective removal, particularly if carried out by abrasive means, involves the expenditure of considerable physical effort, as the required grinder or sander itself may have considerable weight, is typically awkward and clumsy to work with, without benefit of a stabilizing platform or guide not common to such hand tools, and contrary to the need for compactness and portability. Over the course of performing what is typically a physically arduous task in oftentimes challenging work environments, there is an increased possibility of reduced accuracy and consistency in providing the grinding/sanding operation because of the lack of a stabilizing or guiding platform.
More specifically, hand-held tools and especially power tools such as disc grinders employ grinding wheels and cut-off wheels with grinding surfaces or sharpened cutting edges or teeth for grinding, sanding, or cutting all manner of stone, masonry, wood and other material that may be provided in block, sheet, slab or other forms. For example, disc grinders may be used to cut slotted or grooved reliefs at predetermined intervals in solid surfaces such as concrete to serve as stress reliefs during curing and thereafter when the concrete may expand and contract in response to thermal loads provided internally during curing and externally in response to environmental factors. Slots and grooves may be cut through the thickness of the concrete slab to serve as expansion/contraction joints. Alternatively, the slab may be provided with grooves to a subsurface depth, but not the complete depth of the slab for several purposes. One purpose is to serve as scoring lines for separation or demolition purposes. Another purpose is to serve as localized centers for cracking and crazing within the slot so provided, thereby minimizing or preventing the appearance of thermal cracking/crazing at the surface of the slab. Such hand tools may also be used for shaping and cutting other hard and durable material in sheet, slab or other forms, both natural and artificial, including granite, marble, stone and wood, as well as artificially formed materials including slab or sheet stock of solid surfacing materials commonly used for applications including but not limited to foundations, flooring, counter tops, and roofing. Due to the nature of these applications, conventional portable, hand-held power tools are necessarily built with a strong and durable construction, and are hence heavy and cumbersome, requiring significant strength, agility and endurance by the technician or operator for continuing use especially on extended or elaborate projects.
An important problem in the related art, as noted above, is that the technician must continuously balance the tool while guiding it during the material processing operation for essentially the entirety of the cut, so that the grinding wheel remains in substantially the same orientation while in contact with the underlying substrate to achieve the desired cut. The nature of this work again requires considerable strength, endurance and precision, and even a slight loss of any of these attributes by the technician or operator typically results in waste and spoilage of the stock material being cut, in addition to the lost labor and commensurate losses in production time and output. This problem is especially acute in the concrete cutting industry, where the substrate being worked is often large cast-in-place slabs for which inaccurate scored relief lines and grooves can materially and negatively affect subsequent construction requirements, and wherein the cutting saws may be of commercial grade with a commensurately greater weight than those saws provided on the consumer retail level. A related problem is maintaining an accurate cut when guiding the power tool over a surface featuring undulations or other features that challenges the technician or operator in maintaining a perfect cut through the substrate.
Accordingly, there exists a need for an apparatus that enhances the use and performance of portable power tools used in all manner of performing cuts, slots and grooves, and overcomes the substantial shortcomings of the prior art, while maintaining portability and compactness of the portable power tool.
Accordingly, it is an object of the present invention to provide an apparatus for supporting and stabilizing a portable power tool saw to improve operating precision.
It is another object of the present invention to provide an improvement for supporting a portable power tool that may easily and conveniently be retrofitted to conventional portable power tools such as power disc grinders, sanders, and other hand-held power tools for which improved and consistent handling characteristics are desirable.
It is a further object of the present invention to provide an improvement for supporting a portable power tool that is easily and readily affixed and removed by the professional and amateur alike, and once properly installed with the cutting saw, provides consistent cutting results irrespective of a user""s strength or endurance.
It is yet another object of the present invention to provide a support accessory for a power hand tool that is operably affixed to and supported by the hand tool in a manner that negligibly effects its portability and compactness.
It is a further object of the present invention to provide a power hand tool constructed with the present invention.
According to the present invention, an accessory for a power hand tool overcomes the shortcomings of the related art by providing a rolling support structure that enhances ease of handling and operation of the power hand tool for supporting and carrying the hand tool over a substrate at a user-selected or preselected working depth or height of the disc grinder or sander or similar material processor. The accessory includes a support bracket having a longitudinal axis, for attachment to a portion of the housing at an intermediate to position of the support bracket, and a pair of low-friction surface engaging devices such as rollers secured to the support bracket at mounting locations longitudinally separated from the intermediate attachment position. As is common to many power hand tools, the tool housing includes a cylindrical housing portion through which the drive shaft extends for supporting the disc grinding wheel or sanding wheel. The inventive apparatus thus includes a corresponding concavity for being installed about the cylindrical portion of the housing in nesting relationship with a clearance fit or sliding fit therebetween to allow for angular adjustment therebetween.
A curvilinear fastener slot is provided in the support bracket parallel to and radially outwardly spaced from the concavity of the support bracket, and is used to secure the support bracket to the housing at a desired position, when the power tool is adjusted to the desired angular position and vertical height relative to the substrate to be processed, by a fastener securing the support bracket to the housing. Additionally, the rollers are carried on axles supported by the support bracket, and axle mounting slots are provided in the support bracket, each slot being at an angle offset from the longitudinal axis for selectively adjusting the vertical processing position of the material processing disc relative to a substrate when the accessory is mounted to the housing.
A power hand tool constructed with the invention is further disclosed. The tool is driven by an internal (e.g. electric) or external (e.g. compressed air) power source, the tool having a housing supporting a drive shaft driven by the power source, a material processing disc such as a grinding wheel or sanding wheel supported by the drive shaft for operation about a rotational axis, and a support bracket having a longitudinal axis supported by the housing at an intermediate position of the support bracket, with a pair of surface engaging rollers secured to the support bracket at mounting locations longitudinally separated from the intermediate attachment position.
According to the invention, the support bracket may be removably secured to the tool, or integrally formed therewith. Furthermore, for a power hand tool having a cylindrical bearing surface incorporated in its housing, the support bracket includes a corresponding concavity having an axis of rotation for being installed in nesting relationship with the bearing surface. The invention further exploits the type and location of fasteners securing the housings of some power hand tools, whereby the support bracket is secured to the tool by a fastener common to the tool adjacent the housing portion through which the drive shaft projects, further allowing for adjustment of the support bracket in an arcuate manner to a selected position and then securing the bracket by the common fastener. Alternatively, for a power hand tool having a face through which the drive shaft extends, and a drive shaft retaining bracket offset therefrom, a portion of the support bracket is received and supported therebetween in the installed condition.
The rollers used with the support bracket are carried on axles extending from the support bracket, the axles being positionally adjustable in axle mounting slots provided in the support bracket, each slot provided at an angle offset from the longitudinal axis for selectively adjusting the vertical processing to position of the material processing disc relative to a substrate. According to one embodiment of the invention, the offset angle is perpendicular to the longitudinal axis, although other mounting slots with alternate configurations may be provided. Furthermore, to provide additional stability during use of the power hand tool, a pair of rollers may be supported on at least one of the shafts (or even both, if desired), wherein the shaft extends to opposite sides of the support bracket for supporting the rollers in opposing relationship and providing a relatively wide support base.
It should be noted and understood that with respect to the embodiments of the present invention disclosed herein, the materials and apparatus disclosed and suggested may be modified or substituted to achieve the desired protected structures without departing from the scope and spirit of the disclosed and claimed invention.